As an improvement suggestion would be to make a deeper D plate so the wheels and the tool arm are farther apart. This will allow for a person with large hands to work the left side of the platen without hitting the tool arm.

Hi Dan
This would be a great improvement so you could use it as a slack belt as well just need to work out how to remove the platen with the least of amount of tools.
Have you thought of a swivel with 8" wheel and 2" wheel like the one on the no weld grinder plans from usaknifemaker. I hope too knock up a design on Google Sketch Up. Not sure if this will work but not very good at the Autocad I will see what i can do.

The tool arm is part of the issue. The D plate itself is fairly close, if I recall correctly about 0.75" to the D plate and 1.5" to the tool arm end. I don't have a problem grinding up close on the left side, but I have only average (size 9-10) hands. For someone with large hands it could be a problem.

I use the top run between the tracking wheel and top idler on the platen for slack belting. It does get dusty and some people may wish to have that dust heading downwards vs. towards the operator.

These ideas are helpful in making improved versions. Thanks to everyone.